近30年来青海省三江源区草地的土壤侵蚀时空分析

Spatial-temporal Analysis of Soil Erosion in Grassland over the Past Three Decades in Sanjiangyuan Region,Qinghai Province,China

分析了青海省三江源区草地生态系统土壤侵蚀的空间差异,以及草地退化与土壤侵蚀的关系,并对该区近30年来土壤侵蚀的动态变化进行描述。结果表明,该区域微度以上土壤侵蚀面积占源区总面积的46.47%,而草地生态系统发生微度以上土壤侵蚀的面积比例达56.04%。源区土壤侵蚀类型是以冻融侵蚀伴随着水力侵蚀或风力侵蚀的复合侵蚀为主,分别占源区土壤侵蚀总面积的41.93%和20.48%,侵蚀程度以轻度为主。源区土壤侵蚀受垂直地带性和区域地貌格局的影响,水力侵蚀、风力侵蚀、冻融复合型侵蚀分别发生在3 200~4 600m、2 800~3 600m和4 400m以上的海拔范围内,以及5~25°、〈3°与5~15°的坡度范围内,与坡向关系不大。风力侵蚀和冻融复合型侵蚀的程度随海拔升高而呈增加趋势,而水力侵蚀则呈下降趋势。对20世纪70年代中后期-90年代初、90年代初-2004年两个时段土壤侵蚀的比较发现,20世纪90年代以来三江源区的土壤侵蚀状况在前期加剧的情况下更加恶化,而气候暖干化导致的多年冻土退化和长期超载过牧导致的草地生态系统退化是造成三江源区草地生态系统土壤侵蚀加剧的主要因素。

Sanjiangyuan Region,as the headwaters of the Yellow River,Yangtze River and Lancang River,is known as China＇s Water Tower.In recent several decades,continuously grassland ecosystem degradation and soil erosion in the region were increasingly serious due to natural and human activities such as global warming,overgrazing,mining etc.Currently,the degradation of grassland ecosystem has attracted attention worldwide.Therefore,the spatial and temporal patterns of soil erosion in the region were beneficial to provide scientific foundation for ecological protection and construction.This study aims to analysis the relation between grassland degradation and soil erosion,and spatial variations and dynamic of grassland soil erosion in the region since 1970s,according to remote sensing interpretation of soil erosion,land use and grassland degradation information.This paper analyzed spatial difference of soil erosion and its dynamic status over the past 30 years in grassland ecosystem in Sanjiangyuan Region,Qinghai Province.The results showed that the proportion of soil erosion in this region account for 46.74%,and 56.04% in the grassland.The primary types of soil erosion in Sanjiangyuan Region are composition of freeze-thaw and wind or freeze-thaw and water erosion,about 41.93% and 20.48% of total erosion area respectively,and most of the erosion degree is slight.The distribution altitude range were 3200~4600m,2800~3600m and more than 4400m,and the slope range were 5~25°,less than 3° and 5~15° for water erosion,wind erosion and composition freeze-thaw erosion respectively.The erosion degree of wind erosion and composition freeze-thaw erosion increased with elevation rising,and decreased for water erosion.Soil erosion from the beginning of 1990s to 2004 showed more enormous degradation than the former period,and the warming climate and grassland degradation resulted overloading and overgrazing were the main driving forces.